Environment variables are only read during bootstrap

Context

Some values the panel needs, such as secrets, come from environment variables, supplied either through the process environment or through a local env file. They are needed while the panel is being configured. Once it has been, nothing should depend on reading them directly.

Decision

Environment variables are held by Env, a static singleton initialised once during bootstrap from either the $_ENV superglobal or an env file, and it exists only during initial bootstrapping. Initialising it a second time, or reading from it before it has been initialised, throws, and its typed accessors throw when a value cannot be cast to the type requested. Code outside bootstrap does not read environment variables.

Alternatives

No alternatives were weighed.

Consequences

Easier:

• Environment variables are available anywhere during bootstrap without being passed around.
• Reading a variable as a specific type fails loudly when its value cannot be cast.

Harder:

• Nothing in the type system stops code outside bootstrap from reading Env, so keeping it to bootstrap relies on discipline.
• An env file is read into Env alone, without populating $_ENV, so nothing else in the process sees its values.

Constrained:

• Components receive values drawn from the environment through their configuration, not by reading the environment.
• Configuration resolves environment variables while it is loaded.

Sources

• Issue #22, Engine - Config, 2026-03-25: environment variables loaded from the $_ENV superglobal or a local env file.
• Commit c4c9f51, "Initial config work", 2026-03-28, on the branch of PR #25: the first code of Env, which is created.
• Commit 599a0ea, "Introduce an exception around env initialisation", 2026-03-29, on the same branch: throwing when Env is used before initialisation or initialised twice.
• PR #25, feat(config): Add config component, merged 2026-03-29 and squashed as 180794a: Env as merged, which is decided.
• Env being a static singleton by design that exists only during initial bootstrapping, and its typed accessors throwing when a value cannot be cast: first written down on 2026-09-14.
• Issue #31, Engine - Config - TOML, revision of 2026-05-14 in its edit history: configuration resolving environment variables against Env while it is loaded, taken from what followed rather than anticipated.